1. Field of the Invention
The present invention relates to a flat belt which is used for conveying an object on a surface of the flat belt, in particular which is used for conveying paper.
2. Description of the Related Art
The flat belt is used for conveying an object, for example paper, on an outer surface thereof. Conventionally, the flat belt has a belt body including a tension member and a fabric which covers the belt body. The tension member, which is disposed along the pitch line of the flat belt, usually has the great stiffness in order to resist load.
However, the flat belt is not sufficiently stretchable and flexible in the longitudinal direction thereof due to the stiff tension member. Therefore, it is not appropriate that the flat belt is installed on a small pulley (for example when the diameter is less than 25 mm). Namely, when the flat belt is wound and revolved around the small pulley, the belt is broken immediately, for example the fabric is separated from the belt body or the yarn of the fabric in longitudinal direction of the flat belt is cut.
Further, when the object conveyed by the flat belt is printed paper, the ink on the printed paper is sometimes wet, therefore the ink sometimes transfers to the outer surface of the flat belt. If the outer surface consists of a fabric, the fabric is impregnated with the ink when the ink transfers outer surface. In this case, the fabric can hold the impregnated ink to some extent, therefore if the amount of the impregnated ink is little, the impregnated ink is not released from the fabric.
However, if the amount of ink that impregnates the fabric is over a predetermined amount, the fabric can not hold the impregnated ink. In this situation, the impregnated ink in the fabric is transferred to the conveyed paper which contacts the outer surface of the fabric, so that the conveyed paper becomes dirty. Further, it is impossible to remove the impregnated ink from the fabric even if the outer surface is wiped using alcohol etc. Namely, the flat belt can not be used for conveying paper, if the amount of the ink impregnated into the fabric increases more than the predetermined amount.
Furthermore, it is known that a flat belt which has a resin layer as an outer surface, is used for conveying paper thereon. For example, the flat belt has the outer surface consisting of a fluoropolymer resin film, as shown in Japanese Unexamined Patent Publication (KOKAI) NO.2000-136009. In this belt, the wet ink is not easily transferred to the outer surface due to the water and oil repellent proprieties of the fluoropolymer resin. Further, even if the ink transfers to the outer surface, it is easy to remove the ink from the surface by wiping using alcohol because the transferred ink is not impregnated into the fluoropolymer resin. Namely, the fluoropolymer resin film prevents the transferred ink from retransferring to the conveyed paper.
However, the fluoropolymer resin film is very hard therefore this flat belt tends to scratch the paper. Further, a flat belt having a hard film surface is not sufficiently flexible and therefore such a flat belt should not be installed on a small pulley. Additionally, it is easy for the fluoropolymer resin film to separate from the belt body because the adhesion the between the fluoropolymer resin and the belt body is not good.